This invention is a additively manufactured wall panel using computer aided design (CAD) and computer aided manufacturing (CAM) to design and manufacture multi-colored and multi-layered wall panels. This is accomplished through a process that combines precast concrete methods with 3D printing.
Precast concrete has long been known to produce massive wall panels that each weigh thousands of pounds and are thereby expensive to ship and even more expensive to install. Architectural precast is also known for producing attractive exterior wall finishes using different colored concrete and/or colored aggregates. However, architectural precast is one of the most expensive building systems available, costing several times that of most other building systems.
One of the problems with precast concrete is that everything about it is big, heavy and hard and must be handled accordingly. For example, precast concrete is typically a four to eight inch thick solid concrete slab weighing 40 to 80 psf. This results in a 200 square foot wall panel weighing four to eight tons and requiring costly shipping and large cranes for handling and installation. It also results in an expensive, single function cladding to which materials directed to most other wall functions must be job-site attached after the wall panels are installed.
Precast concrete manufacturing is also problematic in that the panels are made using larger sand particles and at least ⅜″ rocks that can be highly abrasive when cast onto forms. This abrasion requires more durable and expensive forms or limits the number of uses of form liners. This is why most precast uses steel forms which results in only flat wall faces or costly steel form fabrication. Precast concrete is also stuck in the tradition of concrete practices which means the wall panels are thick, steel reinforced, heavy and have limited design potential. Finally, precast has design limitations that prevent a much broader utilization of multi-colors and textures.
The process of 3D printing, a/k/a additive manufacturing is a process of making three dimensional solid objects from a digital file. The typical process for 3D printing concrete buildings is well known in the art and is based on CAD/CAM whereby a computer program is used to design a building's walls and a computer controlled robotic arm manufactures them in place or in a factory. Basically the robotic arm is directed by the program to travel along a set horizontal path while extruding a bead of low slump concrete on top of a prior pass of the arm and bead of concrete. The concrete beads are extruded from the arm in a size of about one to three inches in diameter and produce an unfinished, stacked pancakes appearance from the multiple beads laid upon one another.
This 3D printing process leaves much to be desired in that the wall face on both sides are rough and must be textured or otherwise covered and there is no efficient way to provide attractive claddings or multi-color finishes to the walls. The 3D printed walls also provide minimal building wall functions of an enclosure and structural support with all other typically required functions, such as thermal insulation and air, vapor and moisture barriers, separately added. These 3D printed walls also face the unresolved issues of meeting US building codes.
There are multiple processes disclosed by which multi-colored precast concrete has been produced. U.S. Pat. No. 3,145,502A (Rubenstein) disclosed stencils laid over the mold face before spraying a resin face layer and then removing the stencil to spray a resin backing layer. U.S. Pat. No. 4,153,401A (Longinotti) disclosed partition units lowered onto a mold cavity to keep different colored mortar separate during casting, after which the partitions are immediately raised from the mold. U.S. Pat. No. 4,656,722A (Armstrong) discloses a brick pattern form over which a single color concrete is cast. U.S. Pat. No. 5,002,817A (Jones) discloses brick pattern form liner with raised grout dividers and method for forming concrete panels with single color concrete. U.S. Pat. No. 5,735,094 (Zember) discloses a template, i.e. stencil, placed over a first color after which a second color is applied and the stencil removed to expose the first color.
Relative to 3D printing, there are far fewer disclosures that may be applicable to precasting. For example, U.S. Pat. No. 5,216,616A (Masters) discloses system for producing 3D objects from computer generated coordinates whereby a first dispenser places material while second dispenser builds material dividers. U.S. Pat. No. 6,030,199A (Tseng) discloses a method for forming a 3D object by computer control of planar deposition of molten forming materials. DE102006057039 (Parsch Egon) discloses a computer controlled concrete block maker that discharges clumps of different colored concretes in a predetermined shape and position, side-by-side or on top of one another, in a flat faced mold which is then vibrated.
While the present utilization of 3D printing structural walls has much to overcome, the use of CAD/CAM has been successfully implemented in many industries and holds much potential for precast wall panels. A such, there is a need to adapt the CAD/CAM process to horizontally cast, precast wall panels. There is also a need to improve the material efficiency of precast wall panels by using less, although higher quality materials, to produce less costly, lighter and easier to install wall panels. There is also a need to use less abrasive cementitious materials to enable the use of less costly and more versatile forms. There is also the need to improve the effectiveness of precast walls by making them a more comprehensive wall system incorporating insulation, an air, vapor and moisture barriers and simplifying interior finishes. Finally, there is also the need to increase the wall panel's face design flexibility and attractiveness by incorporating more multi-colored designs and textures.